Ground effect vehicles have been developed in both fields of aeronautics and marine craft. Ground effect vehicles are those vehicles which receive reduced drag due to the reduction of wing-tip vortices while traveling at low altitudes near ground, and more typically, near water. The closer the wing tip is to the ground or water, the lower the drag. Ground effect vehicles generally comprise marine craft and aircraft. The two are typically distinguished by those that can sustain extended flight without the aid of ground effect (aircraft) and those that cannot (marine craft). The International Civil Aviation Organization (ICAO) and International Maritime Organization (IMO), both organizations of the United Nations, jointly exercise jurisdiction over these vehicles. The ICAO and IMO have also united to develop uniform navigation and safety rules for these types of vehicles, expected to be published by the year 2004.
The marine engineering arts have developed ground effect craft that either induce ground effect, such as hovercraft, or utilize some benefits of ground effect in combination with hydrodynamic hull and fin arrangements, such as catamarans and hydrofoils. Other maritime ground effect aircraft are being developed, and typically include ground effect wings to provide greater stability and lift. They cannot, however, sustain flight without maintaining close distance to the ground.
The aeronautical engineering arts have also advanced ground effect vehicles beginning with the Russian Ekranoplan KM, also known as the Caspian Sea Monster, which was developed in the 1960s for cargo transport and missile delivery applications. The KM uses extended wings with negative dihedral winglets on each end in order to promote the ground effect. The negative dihedral winglets are generally allowed to touch water if the KM is unintentionally flown too low. However, allowing the winglets to touch the water substantially increases drag, and may damage the wing or winglets. As such, the structural weight of the wing must be increased to account for water loads. If too much of the winglets contact water, the airplane may also experience stability problems.
Hoisington and Rawdon disclose in U.S. Pat. No. 6,547,181 (assigned to The Boeing Company, Seattle Wash.), a ground effect wing having a variable sweep winglet. They describe the winglet as “positionable at a sweep angle to control winglet tip clearance from ground”. They state; “Variable winglet tip clearance reduces the risk of damage or instability due to collision with the ground or water, thereby permitting more efficient flight at lower altitude with an equivalent safety.” Clearly, the reference here is to aircraft flying at very low altitude (in Wing Ground-Effect—W.I.G)
Reslein, in U.S. Pat. No. 5,727,495 1998 discloses an example of an active aeronautically controlled vessel. Such an approach succeeds at 30,000 feet where an operator would have several minutes to regain manual control following a system failure, but at mere meters off the sea surface any failure of such a complex flight system while in ground effect would be catastrophic At one hundred miles per hour and two meters off the sea surface an operator would have less than one quarter of one second to regain manual control. Insufficient time to manually react. Human reflex time generally is too slow to visually anticipate and adjust for varying wave heights.
In U.S. Pat. Nos. 4,505,442 and 4,685,641, Kirsch et al, disclose a transient Air and Surface contact vehicle and a Transient Surface contact vehicle. In both cases, the vehicle is propelled by some form of air propulsion system as opposed to a water propulsion system. The vessels are designed to skim across the water surface on a plurality of adjustable struts. These vehicles share a similar aerodynamic shape and are essentially aircraft designed to fly in close proximity to a water surface. In neither case is any provision made for bank and turn capability nor is there any provision for providing directional stability in the face of random wave surfaces striking the forward struts.
In U.S. Pat. No. 5,026,002, Yarrington discloses an amphibious vehicle having an aerodynamic wing attached to a main fuselage with a centrally positioned channel flow tunnel under the middle thereof. It has at least one large diameter in-fuselage ducted fan assembly is housed in a duct extending through the fuselage and at least one main helicopter-like rotary assembly on a supporting superstructure above the main fuselage. A tail is connected to the main fuselage and has areas appropriate to an anti-torque mechanism. This vehicle is essentially a helicopter designed to fly in close proximity to a water surface. Any ground effect is created by the down force of the fan blade assembly and the supporting foils are designed to leave the water surface at cruising speeds.
In U.S. Pat. No. 5,711,494 Saiz discloses a hydrofoil comprising a flat vessel of aerodynamic profile which, together with small planes, produces an aerodynamic lift, and the broad base of the hull contains a set of flexible fins whose cross-sections reduce from relatively thick inner ends of relatively large cross-section to relatively thin outer ends of smaller cross-section. The fins are inclined rearward to the vessel. Forward motion by whatever air flow propulsion system is used, produces a hydrodynamic lift. This design does not provide for any bank-turn mechanism, anti blow-over tail device, or gyroscopic stabilization system connected to the lift fins.
In U.S. Pat. No. 4,705,234, Bourn discloses a Ram Wing surface effect vehicle having a hull of generally rectangular shape concave at the front underside and contouring to a flat planing hull at the stern, an upper surface forming an airfoil, a passenger/operator's cabin is mounted on top of the hull and support a ram wing and propulsion system. The disadvantages of this design include the use of a high drag horizontal air foil, no capability of responding to variable sea states while at speed, and lack of a blow-over device at the rear. This vessel is not designed to remain in contact with the water at speed, so it is essentially an aircraft designed to fly in close proximity to a water surface.
In U.S. Pat. No. 4,712,630, Blum discloses a ground effect vehicle consisting of a central wing-like support body, floats and/or undercarriage units located on both sides of the support body, a thrust generator located in front of the support body, a control surface and a cabin. This vessel is not designed to remain in contact with the water at cruising speeds and is an aircraft designed to fly in close proximity to a water surface.
In U.S. Pat. No. 5,314,035, Schoell discloses a surface effect vehicle having a pair of lifting scoops or air foils mounted on a vehicle body, one in front and the other in the rear. Each lifting scoop has an arched leading edge to collect air under the scoop to lift the vehicle on a cushion of air. The vehicle has a pusher type engine with a propeller to push the vehicle. There are no movable foils and no facility for bank and turn maneuvering or for dealing with unpredictable wave forms striking the vehicle at speed.
In U.S. Pat. No. 6,230,835, Fischer et al disclose a ground effect vehicle comprising a hydrofoil or hydrofoil outer parts which can pivot about a parallel line relative to the longitudinal axis of the body in order to increase the speed range when flying close to the ground. This craft is designed to avoid touching the water of ground surface and is therefore an aircraft not a marine vehicle.
In U.S. Pat. No. 4,080,922, Brubaker discloses a Flyable Hydrofoil Vessel capable of achieving hull borne, foil borne and airborne configurations. It does not utilize maritime ground effect.
Most inventor/designers of wing-in-ground effect craft vehicles incorporate neither transitional lift assist devices, nor design-integrated flight control hardware other than conventional type systems designed for aircraft. They rely upon traditional aeronautical engineering principals for operation and control. Albeit, with improved wing design for best performance in ground-effect. Note the original marine ground-effect craft patent; Lippisch (1965) U.S. Pat. No. 3,190,582. This was essentially a conventional aircraft, but it also had an airfoil plan optimized for ground effect.
The problem with the application of traditional aeronautical engineering to marine based wing-in ground effect vehicles is that there is currently no widely available civilian technology to produce a vehicle structure light enough to operate in complete free flight, yet sturdy enough to withstand the potential forty −G impact of hitting an eight foot wave at one hundred miles per hour.
Producing a vessel sturdy enough for safe high-speed maritime operation in ground effect will require some form of waterborne lift assist device. Simple ski, or water-plane type devices provide the required additional lift.
U.S. Pat. No. 5,950,559 Klem utilizes a simple forward mounted ski. but will only function effectively within very limited and consistent sea states. In addition. a ski-plane area large enough to provide sufficient lift at slow speed will transmit too great a shock load to the vessel's structure at high speed and likely break it apart. A ski-plane area small enough to provide proper lift assist at high speed will not have enough water-plane area to lift the vessel free and clear of the water for a clean transition to flight mode from low speed water mode. A simple ski on stilts will not have much of a chance of structural survival against severe wave impact loads.
In U.S. Pat. No. 4,095,549. Williams discloses a solution for air/water interface device for ground effect craft while in high speed cruise mode. However, without variable geometry foil control. and retractable foil appendages, this design presents the opposite problem of the simple ski design. There is no bank turn ability for safe high speed maneuvering. The additional drag induced by the fixed, extended foils during the critical transition phase between high drag water born operation. and low drag airborne cruise mode, requires more installed horsepower than would be commercially viable. Extra engine weight and fuel burn will be too high for economic operation. It has also been found in ocean based model tests that this, and other designs, one foil forward, two aft; tricycle gear layout also causes lateral control problems as the single forward foil launches off to either side of uneven wave crests.
Thomas A. Edison Lake, U.S. Pat. No. 1,846,602 disclosed a two foils forward with one aft tail dragger configuration that tests have proven to provide the best response over variably sloping wave crests. He disclosed a form of variable geometry with freely hinged water planes. Without attack angle control however, and no variable foil geometry to gradually and automatically reduce water plane area with speed increases, pounding in a seaway would be significant and destructive as it would be to any flat ski design. The jet powered Convair Sea Dart design decades later drew upon Edison Lake's plan form and flat skis, but as a supersonic military fighter it was impractical for passenger transport.
In U.S. Pat. No. 3,762,355 Raynes discloses a Water Craft with Aerodynamic lift propelled by an aircraft engine which rides on retractable skis. This design is not capable of bank and turn control.
Japanese Patent No. 62-152960 A discloses a craft built as a conventional aircraft with retractable skis or foils. This design is not capable of bank and turn control and is subject to the frailties of aircraft construction in a marine environment.
In Russian PCT patent PCT/RU92/00238, the inventor discloses an AIR-CUSHIONED FLYING VEHICLE using retractable skis. This design is not capable of bank and turn control and is subject to the frailties of aircraft construction in a marine environment. The form of the skis is such that they taper and are wider away from the direction of travel whereas the present invention discloses the opposite foil configuration.
The following additional patents are cited in this application
United States Patents:
U.S. Pat. No. 2,722,189 Hobday—Nov. 1, 1955
U.S. Pat. No. 1,720,167 Clifton—Jul. 9, 1929
U.S. Pat. No. 2,364,676 Warner—Dec. 12, 1944
U.S. Pat. No. 3,132,619 Lopez—May 12, 1964
U.S. Pat. No. 2,795,202 Hook—Jun. 11, 1957
U.S. Pat. No. 2,972,974 Follett—Feb. 28, 1961
DES. 226,783 Lewis—Apr. 24, 1973
U.S. Pat. No. 3,627,235 Lippisch—Dec. 14, 1971
U.S. Pat. No. 3,661,111 Lippisch—May 9, 1972
U.S. Pat. No. 3,830,448 Lippisch—Aug. 20 1974
U.S. Pat. No. 3,952,678 Weston—Apr. 27, 1976
The present invention seeks to improve on these and other prior art references by providing a vessel utilizing the advantages of maritime construction with some aeronautical technology and construction methods to provide an economical and practical means for a synergy between what have been previously disparate arts.